It's a mode of the Delay block. Enter Edit mode and there are controls on the 2nd page.
You can also assign these to a midi foontrollers, the CC's are in I/O > Ctrl. Page 53, manual.
The looper is an option type in the delay block. Once that page is open and displayed on the Axe-Editor, the control functions are a group of on/off switches for Record, Play, Stop, etc. The next challenge is to figure out how to assign midi CC values to the switches. HELP!!! anyone?
For the sake of anyone else reading this thread who doesn't know this, we should point out that this is pnly a feature in the Ultra 9not the Standard Axe FX).